The high bandwidth inherent in cable television systems makes such systems attractive candidates for providing communication links for accessing the Internet. Cable television systems provide a high bandwidth communication path for delivering information from the cable headend to the cable subscribers. While this bandwidth is currently used primarily for delivering television programming, it can also be used for delivering information received over the Internet.
The typical Internet user requires a much larger incoming bandwidth than outgoing bandwidth. Typically, a user is requesting information from a server on the Internet. The amount of information returned is usually much larger than the message specifying the information. For example, a user requesting a file containing a picture sends a message to the server of only a few hundred bytes of information and receives back a message containing the file which may be hundreds of thousands of bytes of information.
This type of communication is well suited for cable television systems. Such systems have low bandwidth paths from the cable subscribers to the cable headend and high bandwidth paths from the cable headend to the subscriber. The low bandwidth paths are currently for ordering pay-per-view programming.
In principle, the installation of digital services on a cable television system requires only the installation of the appropriate modem at the subscribers location. However, in most systems, the low bandwidth path from the subscriber's premises to the cable headend has not been tested. The cable network is, in general, a tree and branch network with the cable headend at the root node of the tree and the various subscribers at the leaf nodes of the tree. The communications path from the cable headend to the subscriber premises are, in general, known to be functioning properly, since any communications path problems in this direction are detected by the user when he or she attempts to watch television. Further, noise sources at one subscriber's location do not interfere with the reception at a second subscriber's location.
Communications from the subscriber's premises to the cable headend are more problematical. The communications in each direction are isolated from one another; hence, there is no assurance that the path from the subscriber to the cable headend is operational even when it is known that the path from cable headend to the subscriber is functioning properly. The path from the subscriber to the cable headend includes various amplifiers and couplers which also affect the communications in the direction from the subscriber to the cable headend. A failure in one of these components can lead to a failure in the communication path from the subscriber to the cable headend while leaving television reception at the subscriber in tact.
In addition, noise sources at the various subscriber locations are combined in a funneling affect at each branch of the tree structured network. Hence, the cable headend receives a signal that includes the additive noise generated by each subscriber. Hence, a noise source at one subscriber's location can interfere with communications from all subscriber's on the network.
These problems make it difficult to debug a new communication path from the subscriber to the cable headend. A technician debugging a new service connection in the field utilizes a testing system having one component at the cable headend and one component that the technician attaches at different locations in the communications path. The two components attempt to communicate with one another to run various tests designed to isolate problems and align the system amplifiers. If the subscriber component does not receive a response to a message sent by it to the cable headend, the technician has no way of determining if the lack of response is due to noise in the path from the subscriber location to the cable headend, a break in that path, someone has turned the cable headend component off, etc.
Broadly, it is the object of the present invention to provide an improved testing system for bi-directional communication systems.
It is a further object of the present invention to provide a testing system that provides the technician with information about the source of the problem that leads to a lack of response to a message from the subscriber location to the cable headend in broadband communication networks and the like.
These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description of the invention and the accompanying drawings.